<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Font</title>
    <style>
    </style>
</head>
<body>
    <div id="container">Font</div>
    <div id="defaultFixedFontSize" style="font-family: Courier New">DefaultFixedFontSize</div>
</body>
<script>
    function getFontFamily(){
        return window.getComputedStyle(document.body).fontFamily
    }

    function getDefaultFixedFontSize(){
        return (window.getComputedStyle(document.getElementById("defaultFixedFontSize"), null)).fontSize
    }
</script>
</html>